As a rule, a protective film for preventing wear is formed on the surface of a magnetic head for use in a hard disk drive or the like (see, e.g. Japanese Application Publication No. 2002-279605). In a technique described in this document, a silicon film is formed on a substrate of the magnetic head by a sputtering process, a DLC film is formed on the silicon film by a CVD process, and a ta-C film is formed on the DLC film by a filtered cathodic vacuum arc (FCVA) process.
Additionally, a silicon film is formed as a contact layer on an air bearing surface (ABS) of the magnetic head, and a protective film is formed on the silicon film by FCVA process in some case. In this case, when a high bias voltage is applied in order to enhance hardness, the silicon film is mixed with a carbon film, and Si moves toward a surface of the magnetic head, which degrades the wear resistance. Further, the surface energy of the above overcoat layer is high due to the bigger silicon atom dimension will lead bigger distortion or stress in DLC film. In addition, such overcoat layer with multiple films has thicker thickness which will increase fly height of the magnetic head to weaken the performance of HDD.
Therefore there is a need for an improved manufacturing method of a head slider coated with DLC to overcome the above-mentioned drawbacks.